Two-photon decays and transition form factors of ${\pi }^0$, $\eta$, and ${\eta }^{\prime }$ in large-$N_c$ chiral perturbation theory

Patricia Bickert, Stefan Scherer

We present a calculation of $P\to {\gamma }^{(\ast )}{\gamma }^{(\ast )}$ processes, where $P={\pi }^0,\eta ,{\eta }^{\prime }$, at the one-loop level up to and including next-to-next-to-leading order (NNLO) in large-$…